Method of constructing well screens



Jan. 1, 1946. Q OR 2,392,263

METHOD OF CONSTRUCTING WELL SCREENS Filed July 8, 1942 Patented Jan. 1, 1946 s'rATEs] METHOD 01" OONS'I'RUCTING-WHL SCREENS Cheater a. mm, Columbus. on

Application July 8, 1942, Serial No. 450.11:

5 Claims. (c1. 111-98) f This invention a directed to a method of. constructing well screens of a more or less particular type, whereby to increase the effectiveness and prolong the operative eillciency of the screen and particularly of the gravel-wall element of the screen.

The so-called gravel-wall wells, where successive layers of pebbles or other aggregate are arranged in successive layers of outwardly decreasing pebble size surrounding the metallic screen proper, were originally formed by delivering the successive masses of pebbles in loose bulls after positioning the metallic screen in the well. pebbles in such mass and loose delivery, coupled with the fact that the effectiveness of the screening properties. particularly as to required volume of delivered water, were largely, if not entirely, dependent on the skill and knowledge of the operator, in determining the character and disposition of the filtering gravel wall in' accordance with varying conditions of water-bearing sands and freedom of water flow,

soon demonstrated that improvement in making up this type of screen was to be desired. This resulted in a now accepted type of what might be termed a preformed screen, that is to say, the complete gravel-wall screen was completed at the factory, or at least above and beyond the well, and handled in trans ortation and delivery into the well as a complete fixed unit. In

this typ of well screen, the gravel or pebbles of The inability to properly control the.

and preformed arrangement and seriously interferes with their filtering capacity and particularly with the volume output of the well.

The present invention is designed to overcome or prevent the water eflect on the cementitious material, with the end to maintain the screen, and particularly the gravel-wall formation, in its preformed and predetermined condition during its full use in the well.

The improved method consists in applying to the gravel area of the screen, constructed for example on the general lines of the patent referred to and after the same has completely hardened in unit form, a liquid or semi-liquid material which will cover and protect the cementitious material from the recognized d-issolving or disintegrating efiect of the water.

Following the application of the protective material, the screen is subjected to a centrifugal force, as by more or less rapid revolution, to

. cause any and all portions of the protective ma- The composite screen thus became a rigid unit,

which could be handled, transported, and delivered into the well without liability of any change in its gravel-wall filtering ca acity. This type of construction at once presented important advantages over previous types of gravelwall wells. The gravel or pebbles could be selected' both in size and thickness of layers for the best results in a particular type of well: the selected pebbles could be arranged to afford the maximum or any desired filtering ca acity; and the gravel could be arranged in sharply defined layers as to size grouping, so that the smaller outer pebbles could not choke the interstices between theinner larger pebbles: and the entire mass arranged in selected and desired form in a' rigid unyielding unit. Patent No. 1,992,718

- issued February 26, 1935, to the present appli- This tends to disturb their predetermined terial to be driven out of the previously-arranged interstices of the gravel wall, to insure complete or practically complete clearance of the vital water passages through the gravel wall.

In order to more graphically describe the method, the accompanying drawing of a preformed screen illustrates in Figure 1, a perspective view of a complete screen, and in Figure 2, a transverse section of the same.

Figure 3 is an enlarged diagrammatic view showing the pebbles with the application of the fixing cement coating, the latter being exag gerated for a clear illustration.

Figure 4 is a similar view showing application of protective coating, also exaggerated.

Figure 5 is a similar view after clearing excess protective coating.

The illustrated screen presents two layers of gravel or pebbles, the inner layer I being of largersized pebbles than the outer layer 2. The gravel of the respective layers are applied in definite order to insure desired screen eilect with desired spaces between adjacent pebbles for water passage. The inner layer is applied to the inner or metallic screen 3, the form and construction of which is not important for the pu p es of the present invention.

The various layers of pebbles are assembled to provide the screening and volume delivery for the well in which the screen is to be used, and obviously any desired relative sizes of pebbles and number of layers of pebbles 01' different izes may be'employed.

The pebbles are coated with a cementitious material 4 in suillcient volume to insure that adjacent pebbles, when the cement is hardened, will remain in the exact or substantially exact posi tions in which they are applied, as in Figure 3. The completed screen is a rigid unit which may well with the assurance that the filtering gravel wall will remain more or less exactly in its 'preformed and predetermined condition. I

In some water wells, the water is found to contain some elements tending to dissolve or disintegrate the cementitious material employed in making up the screen as previously described. To overcome this obiection, the screen, as shown in Fig re 1, and after hardening. is coated with a material as 5. Figure 4. to protect the cementitious material being afiected by the water. This material, such as a bituminous or asphalt preparation, is ap lied by dippin the screen in the material, or spraying or pouring the material onto the screen. The. manner of application is not important 'so long as the primary obiect. that of p otecting the cementitious material of the screen with a protective coating of the material, is accomn'ished.

During practically any t pe of ap l c tion of the protective material. such material will accumulate in the interstices of the screen formed by the pebbles. and this would of course materially interfere with the efflciency of the screen. To remove this accumulat on without dislodging the protective coating of the cementitious material, the completed and coated screen is subjected to a revolving action, with the result that the developed centrifugal force quickly and efiectively dislodges the protective coating material from the interstices of the screen, and thus clears the filtering area to its original capacity, as shown in Figure 5.

The completed screen will thus remain completely eilective even where the water passing through the screen is of a character which would. in the absence of the protective coating, tend to dissolve the cementitious material used to fix the pebbles in place.

While the above description is complete as to disclosure of the type of well screen to which the invention is applied, it will be apparent, particularly from the appended claims, that the present invention is in efiect a methcdof, first, treating a preformed, gravel-wall well screen to prevent disrupting action on the cementitious material employed in presetting and fixing the gravel of the gravel wall by the water of the well, and, second, forcing the excess of such treating material from the screen to insure desired clearance of the vital and necessary interstices formed by the associated gravel making up the wall.

It will of course be apparent that the primary purpose is to cement the gravel in place with the strongest'practical material, and it is also obvious that after the cementing of the gravel in place to form the gravel wall well of the character designed, the coating or protective material that is to be applied will, in addition to its protective function, although to no small degree, increase the strength of the cementitious connection of the pebble formation. It is to be particularly understood that no limitation is intended by the specific description herein as to the character or nature of 1 the cementitious material, or as to the character or nature ofthe coating and protective material, so long as each performs the desired function and purpose as outlined. The centrifugal force by which the interstices of the gravel wall are cleared and by which the excess quantity of the coating or protective material is removed, may obviously be provided in any desired, conventional, or selected method. Furthermore, any means, particularly any conventional means, may be employed for removing the excess coating material whether or not centrifugal force is used for such purpose.

It will of course be apparent that the protective coating will more or less seal the pores of the cement, but it is to be understood that if desired a relatively thin initial protective coating may be applied to seal the pores of the cement. followed by a second thin coating of the same, or another protective coating appliedover the first protective coating to seal-the pores, if such exist, of the first coating. This variation is contemplated as within the spirit of the present invention for the primary purpose is a protective sealing of the cement. regardless of the material or of the number of coats necessary to properly efiect this purpose.

In making up the screen, the respective layers of pebbles I and 2 are each preferably surrounded by screen-cloth sections i. indicated clearlyin Figure 2. These sections are not intended for-permanent use, but are intended and do provide temporary reinforcement, and the sections are made or a material which will, in the use of the screen or during a definite period after completion of the screen. corrode and disappear. The sections 8 are thus of value for temporarily reinforcing the pebble layers and maintaining same in place during transportation and installation of the screen. The sections I thus permit the screen as a whole, to be shipped to the job in a relatively shorter time after completion, as without such sections 6, the completed screen would have to be held for a relatively .longer setting-up and hardening period before it could be safely shipped and installed.

What I claim is:

1. A method of treating a preformed cemented gravel-wall screen to prevent deleterious efiect of the water on the cement fixing the gravel in place, consisting in applying a coating of a material of the class consisting of bitumen and asphalt. and subjecting the coated screen to movement to develop a centrifugal force to clear. the interstices of the gravel wall of accumulated coating material.

2. A method as defined in claim 1, wherein the application of the coating is by dipping the cemented screen in the coated material.

3. A method as defined in claim 1. wherein the application of the coating is by spraying.-

4. A method of treating an otherwise completed cemented gravel wall screen to prevent deleterious eiiect of the water on the cement of the completed screen consisting in firstcoating the completed screen throughout the gravel wallarea thereof with a material capable of adhering to the cement of the completed screen and having as an essential characteristic the protection of the cementitious material of the completed screenagainst any influence of the water passing through such completed screen to break down the effective cooperation of the cement and gravel of the completed screen, and then subjectingthe screen to a mechanical movement tending to develop suificient centrifugal force to clear themterstices of the gravel wall of the completed screen of the major-portion of the coating material otherwise tending to clog the interstices of such completed screen.

3 5. A method as defined in claim 4. Wherein'the additional liquid protective coating isapplied ina successive layers.

CHESTER E. RECORDS. 

